Developer recounts why agents ignored his MCP tool

On 2026-11-05, the AI section of DEV Community published a retrospective by a developer who spent a summer trying to get a coding agent to follow the conventions of a codebase that nobody had ever written down. His starting premise was that every codebase carries hidden rules: one package always checks rows.Err() after iterating, another logs through slog and never log.Printf, every method on Store names its receiver s, tests in one directory use testify while tests elsewhere use the standard library. In his view, AI coding agents break these rules constantly not out of carelessness but because the rules are invisible to them, living in the statistics of the code rather than in any file. The conventional remedy, he notes, is to write such rules down in a CLAUDE.md or similar file. His first approach was instead to build a MCP server that mined the repository's conventions and exposed them as a tool called get_style_context. The tool went unused: the agent never called it on its own. The author says his first two attempts both failed, and that how they failed is the point. The piece gives no further detail on what the alternative approach he switched to actually was, and offers no quantitative data on tool calls or agent behavior.